1. Field of the Invention
The invention relates to a tamping device for soil compaction, in particular to a vibrating tamper.
2. Discussion of the Related Art
A tamper customarily comprises an upper mass having a drive and a lower mass which has a soil contact element and is movable relative to the upper mass. A tamping system (vibration-exciting device) which is drivable by the drive acts between the upper mass and the lower mass and can be used to bring about the working movement of the soil contact element. Tampers of this type are an indispensable aid on building sites. The function thereof is dependent on energy sources (a combustion drive or electric motor drive) and on countersinking (of the contact element with respect to the soil) and on the mechanical structures of the tamping system, such as, for example, the mass ratios of the moving and non-moving parts, the transmission ratios, the springs (steel or pneumatic), the dampers, the crank radii and the contact elements of the tamping system with respect to the soil.
It is known that tampers operate better on certain soils than on other soils. For example, a tamper first of all operates uniformly on a non-compacted, compactable soil, but, as the soil density increases, falls out of step. This “falling out of step” is expressed, for example, by an empty strike following three working strikes of the tamping foot (soil contact element) because the spring-mass system is no longer in synchronization. In the event of an asynchronous operation of this type, the passive system (upper mass, gripping frame for the operator) reacts with high amplitudes, which makes the guidability of the tamper more difficult.
In addition, the operator is put under considerable stress by the guiding of the tamper, wherein the hand-arm accelerations reach increased values and, as a result, reduce the permitted use period of the apparatus. In addition, the tamper operates at weak power and therefore the soil can scarcely still be compacted.
Furthermore, the mechanical system is highly stressed by the high movement amplitudes of the upper mass that occur during the asynchronous operation, which may result in the mechanical assemblies being overloaded and in the apparatus failing.
This non-uniform behavior of a tamper on different soils becomes all the more serious, the more power it is possible for the apparatuses to output into the soil. Apart from being determined by the drive itself, the power output is determined in particular by the masses, the tamping frequency and primarily by the strike of the tamping foot. In order therefore to be able to provide universally usable tampers, it is known to limit the stroke of the tamping foot to values at which the tamper can still be readily controlled. Impermissibly high movement amplitudes can thereby be avoided. On the other hand, however, the usable compaction power of the machine is also limited as a result because—given appropriately compactable soils—the entire power capacity of the tamper cannot be utilized.
DE 10 2007 048 980 A1 discloses a soil tamping device having adaptive drive regulation.